Fuel injection system for a multi-cylinder engine

ABSTRACT

A fuel injection system for a multi-cylinder internal combustion engine, which includes a rigid elongated unitary member incorporating a gas supply duct, a fuel supply duct and a fuel return duct, each of which extends in the direction of elongation of the unitary member. A separate fuel metering device and fuel injecting device is provided for each engine cylinder. The fuel metering device is arranged to deliver metered quantities of fuel to the fuel injection device and is in communication with the fuel supply and fuel return ducts so that fuel can be circulated through each of the fuel metering devices. The fuel injecting devices are each in communication with the gas duct and communicable with one of the engine cylinders. The fuel injection devices are adapted to effect delivery of a metered quantity of fuel entrained in gas supplied from the gas duct when the fuel injecting device is in fluid communication with a cylinder.

This invention relates to a fuel injection system for internalcombustion engines having two or more cylinders and wherein meteredquantities of fuel are delivered to the respective cylinders entrainedin a gas, preferably a combustion supporting gas, such as air.

It has previously been proposed to deliver a metered quantity of fuel toan engine entrained in a body of gas, with the pressure of the gas beingsufficient to effect delivery of the fuel either directly into thecylinder of the engine or into the induction system through which theair charge passes for delivery to the cylinder. This form of fuelmetering and injection requires the supply of both fuel and gas to eachmetering and injecting unit associated with the respective cylinders ofthe engine. Also, most fuel metering devices require the fuel to becirculated therethrough to prevent the collection of fuel vapourtherein. Accordingly, in a multi-cylinder engine, having an individualfuel metering device for each cylinder, it is necessary to provide forfuel to be returned from each fuel metering device to the principal fuelsource, such as the fuel reservoir. Further, it is normally necessary toprovide a substantially fixed pressure differential between the fuelsupply and the gas supply, as this differential is relevant to themetering characteristics of the fuel metering device, and variationstherein can result in inaccuracy in the fuel metering process.

Because of manufacturing cost considerations, it is customary to providea single pump which provides the fuel circulation from a fuel reservoirto each of the fuel metering devices, with appropriate return lines tothe fuel reservoir from each metering device. Also it is customary forcost saving reasons to provide a single pressure regulator to controlthe pressure differential between the gas and the fuel as supplied toeach fuel metering and injecting unit. This construction results in amultitude of fuel lines between the fuel metering and injection unitsand the fuel pump, and between said units and the pressure regulator,which significantly contribute to manufacturing costs. It will beappreciated that in this construction the fuel and gas lines must beprovided with suitable end connectors, which are usually threaded inorder to provide an effective leak proof connection, and the provisionof complementary threaded components on the fuel metering and injectingunits, fuel pump and pressure regualtor. The manufacture and assembly ofthese multiplicity of threaded components is a further cost factor. Alsoadditional costs are involved in the installing of the numerous fuel andgas lines. Further the multitude of fuel and gas lines detract from theoverall neatness of the installation.

The use of the number of lines for the fuel and gas also presentoperational disadvantages as the resilient nature of the plastic linesusually used results in variations in line cross-sectional area withinternal pressure, and so it is difficult to maintain the requiredcontrol of the pressure differential between the fuel and gas supplies.

In many engine applications, such as automobiles and outboard marineengines, the physical size of an engine and its associated accessoriesis of major importance. There is limited scope for reduction in the sizeof the engine itself, and accordingly it is important to maintain to aminimum the extent that accessories, added to the basic engine, increasethe overall size thereof.

In the light of the above discussed construction, operational and costdisadvantages of currently known fuel injection systems, it is theobject of the present invention to provide an improved system wherebythese disadvantages are at least reduced so as to provide a moreeffective operational system and to also reduce the manufacturing andinstallation costs of the system.

With this object in view, there is provided according to the presentinvention a fuel injection system for a multi-cylinder internalcombustion engine comprising a rigid elongated unitary member havingformed therein a gas supply duct, a fuel supply duct and a fuel returnduct, each said duct extending in the direction of elongation of theunitary member and each adapted for connection to a gas supply, a fuelsupply and a fuel return respectively, at least one fuel metering andinjecting apparatus for each cylinder of the engine each integrated withthe unitary member and each comprising a fuel metering means and a fuelinjecting means, the fuel metering means being adapted to delivermetered quantities of fuel to the fuel injecting means, each fuelmetering means being in communication with the fuel supply and fuelreturn ducts so that in use fuel can be circulated through each fuelmetering means, and each fuel injecting means being in communicationwith the gas duct and communicable with a respective cylinder directlyor induction duct communicating with a respective cylinder of theengine, each said fuel injecting means being adapted to effect deliveryof the metered quantity of fuel entrained in gas supplied from the gasduct when the fuel injecting means is in communication with the cylinderor induction duct.

Conveniently there is also integrated with the unitary member a pressureregulating means which controls the pressure differential between thefuel in the fuel supply duct and the gas in the gas supply duct betweenpre-determined limits. Preferably the pressure regulating means controlsthe rate of return of fuel from the return duct to a fuel reservoir andso regulates the pressure of the fuel in the fuel supply duct. It ispreferable that the pressure of the fuel delivery to the fuel supplyduct is such that the regulating means is required to return fuel to thereservoir over substantially the whole range of operating conditions ofthe engine. This ensures circulation of fuel through the fuel meteringmeans is maintained to thereby reduce the possibility of an accumulationof fuel vapour in the fuel supply or return ducts. The presence of suchvapour, apart from creating a vapour handling problem in relation toemissions control, also contributes to the effective maintenance of therequired pressure differential between the fuel supply and the gassupply.

Conveniently each fuel metering means has a body with spaced fuel inletand fuel outlet ports and the fuel metering means body extends into theelongate unitary member in a direction transverse to the direction ofelongation of the unitary member so the fuel inlet port is located inthe fuel supply duct and the fuel outlet port is located in the fuelreturn duct. Each fuel metering means body has a fuel metering portthrough which the metered quantity of fuel is delivered, and preferablyeach fuel metering means body is located so the fuel metering portdelivers the fuel into a respective fuel cavity located within theunitary member, each fuel cavity being in communication with the gassupply duct. The fuel cavities may be formed in the unitary member ormay be part of the fuel injecting means that extends into the unitarymember.

Preferably the fuel supply and return ducts and the gas duct arearranged so that the fuel metering means body projects into the unitarymember in a direction inclined to the direction that the fuel injectionmeans projects into the unitary member. Conveniently each fuel meteringmeans body extends into the unitary member from one side thereof andeach fuel injecting means includes a body that extends from another sideof the unitary member so as to be located generally at a right angle tothe fuel metering means body. This arrangement contributes to containingthe extent by which the componentry of the fuel injection systemincreases the overall outside dimensions of the final engine assembly,as at least part of the body of the fuel metering means and/or the fuelinjecting means body may be located within the elongated unitary member.

Preferably each fuel cavity is a passage formed within the unitarymember located to receive the metered quantity of fuel from the fuelmetering means and to deliver it to the fuel injecting means.Conveniently the arrangement is such that the fuel is delivered into thefuel cavity at a level above the fuel injecting means so gravity willassist in the transporting of the fuel to the fuel injecting means.Preferably the fuel cavity communicates with the gas supply duct at alevel above that of the entry of the fuel to the cavity so the flow ofgas from the gas supply duct to the fuel injecting means will promotethe flow of fuel to the fuel injecting means. The fuel cavity may beconfigured to present, opposite the location of entry of the fuel, aface inclined to the trajectory of the incoming fuel so the fuelrebounding off that face will be deflected toward the fuel injectingmeans.

The above discussed construction incorporating a unitary rigid memberproviding fuel and gas to a plurality of fuel metering and injectingmeans, each servicing a respective cylinder of a multi-cylinder engine,substantially reduces the number of fuel and gas lines required in theinstallation. In particular, only a single fuel supply line from thefuel pump and a single gas supply line from the pressurised gas sourceare required to service all of the fuel metering and injecting means.Further only a single fuel return line is required from the unitarymember to the fuel reservoir for by-passing excess fuel. Apart from thesubstantial improved appearance which arises from this construction, thereduction in the number and length of resilient fuel and gas linessubstantially reduces the effects on metering accuracy arising fromvariation in the cross-section of these lines with variation of thefluid pressure therein. In addition the number of fuel and gasconnections required to be made is substantially reduced, whichcontribute to both space savings and cost savings and to a reduction inthe potential areas of leakage in the system.

Further, it is possible by the use of a rigid elongate unitary membercarrying a number of fuel injecting means, one to be associated witheach cylinder of the multi-cylinder engine, to use the rigid elongateunitary member as a holding down bar that clamps the fuel injectingmeans in the required assembled relation with the respective cylindersof the engine. Accordingly, the need to provide individual threadedholes for the securement of the respective fuel injection means to eachcylinder is avoided, and a lesser number of threaded holes is requiredto hold the rigid elongate unitary member in clamping relation with thefuel injection means and the engine structure to maintain all of thefuel injecting means in the required operating relationship to theengine.

A number of operational factors must also be considered in the design ofthe metering and injecting unit, including such factors as the weight ofthe valve controlling the delivery of fuel, including the valve stem, asinertia loadings and valve bounce are important in the maintenance ofaccurate fuelling. Also the extent of the surfaces wetted by the fuelafter it has been metered influences the variations in fuel quantitydelivered to the engine on a cycle to cycle basis, and the response ofthe engine to changes in the metered quantity of fuel. There is also thenecessity to protect the fuel metering and injecting unit from heatbuild-up that may damage electrical components and/or lead to fuelvaporisation or other hot fuel handling problems.

It is therefore desirable to provide apparatus for delivering fuel to aninternal combustion engine that is small and compact and will operatewith the required reliability, accuracy and durability demanded withmodern engines.

There is therefore proposed a fuel injection system for an internalcombustion engine comprising a body having an internal port cavity, aport in the body providing communication between the port cavity and theexterior of the body, valve means to selectively open and close saidport, said valve means including a valve element adapted to co-operatewith the port to close same and a valve stem attached to the valveelement and extending through the port cavity, selectively energisableelectromagnetic means within the body disposed about and operablyconnected to the valve stem whereby the valve element is displaced toopen the port when the electromagnetic means are energised, a passagethrough the valve stem communicting the port cavity with a fuel cavitylocated at that side of the electromagnetic means opposite to the port,metering means to selectively deliver fuel to the fuel cavity, and meansto supply gas to the fuel cavity at least when the port is open toconvey fuel from the fuel cavity through the valve stem passage and theport cavity to and through the open port.

Conveniently the electromagnetic means is in the form of a solenoidhaving a coil disposed concentric to the valve stem with a co-axialarmature attached to the valve stem. Preferably the armature extendsinto, or is located substantially within, an annular space between thecoil and the valve stem. The valve stem is preferably of tubular formwith the valve element secured to one end and the other end open toreceive the fuel. At the valve element end communication is providedbetween the interior of the tubular valve stem and the port cavity.Preferably the communication is arranged so a significant quantity offuel may not be trapped in the tubular valve stem below the point ofcommunication with the port cavity and so not pass into the port cavity.Conveniently the fuel may be injected from the port directly into acombustion chamber of the engine.

In the above proposed construction, a number of benefits arise in theoperation of the fuel injection system. The passing of the fuel througha passage in the valve stem, such as is provided by the tubular valvestem, reduces the surface area to which the fuel is exposed as it passesfrom the point of metering to the port through which it is delivered tothe engine, particularly in comparison with prior constructions wherethe fuel has passed through an annular passage. The surface area wettedby the fuel influences the delay that may occur between the variation ofthe fuelling rate at the point of metering and the consequent variationat the port where the fuel is delivered to the engine. During eachinjection cycle, and with changes in fuelling rates, there is a changein the thickness of the film of fuel adhering to the surfaces over whichthe fuel passes from the metering point to the port. Accordingly, if thesurface area in contact with the fuel is reduced there is a reduction inthe total quantity of fuel involved in changes in thickness of the fuelfilm. This is reflected in an improvement in the response time of theengine and a reduction in instability of the engine arising fromvariability in the quantity of fuel delivered between each cycle of theengine.

There is also a benefit arising from locating the electromagnetic means,such as the solenoid assembly, between the injection port and the fuelmetering point, as compared with previously proposed constructionswherein the fuel metering point is between the solenoid and theinjection port. The resulting reduction in the length of the valve stemreduces the weight theeof, and reduces the natural frequency of thevalve stem, and hence reduces the amount of valve bounce that may occuron valve closure. The relatively large quantities of fuel passingthrough the valve stem when the engine is operating at high loadsprovides a significant cooling effect on the solenoid at a time when therate of heat generation is high.

Also, location of the solenoid assembly between the injection port tothe engine and the metering point, and the symmetric external shape ofthe solenoid, enables that portion, or part thereof, of the fuelinjection apparatus to be recessed into the head of the engine to whichthe apparatus is fitted, thereby providing a reduction in the overallheight of the engine and injector apparatus assembly. This location alsoprovides the ability for thefuel to be raised in temperature by heatinput from the cylinder head, particularly at low fuelling rates, andwill assist in atomisation.

The invention will now be described with reference to the accompanyingdrawings, which depict one practical arrangement of a fuel injectionsystem incorporating the present invention.

In the drawings,

FIG. 1 is a perspective view of a typical three cylinder engine having afuel injection system of the present invention fitted thereto;

FIG. 2 is a transverse sectional view of the fuel and gas rail at thelocation of a fuel metering and injecting unit;

FIG. 3 is an axial sectional view of fuel injecting unit and anadjoining portion of the fuel and gas rail;

FIG. 4 is a view of the air control ring in the direction 4--4 in FIG.2;

FIG. 5 is a sectional view of an engine cylinder head with the fuel andgas rail and the fuel metering and injecting units installed thereon;

FIG. 6 is a sectional view of a pressure regulator fitted to the fueland gas rail;

FIG. 7 is a fragmentary sectional view of portion of the pressureregulator along the line 7--7 in FIG. 6;

FIG. 8 is a fragmentary sectional view of an alternative arrangement ofdirecting the fuel and air into he fuel cavity.

Referring now to FIG. 1 of the drawings, the three cylinder two strokecycle engine depicted therein is of basically conventional construction,having a cylinder block and crankcase unit 1, a detachable cylinder head2, and an air induction system 4 on one side of the cylinder block andan exhaust system 5 on the opposite side of the block. Fitted to thecylinder head 2 are respective spark plugs 7, one for each cylinder ofthe engine. Extending generally centrally along the top of the cylinderhead is the fuel and air rail unit 11 attached to the cylinder head bythe mounting bolts 8.

The fuel injection system for the engine as shown in FIG. 2 comprisesthe air and fuel supply rail unit 11, with a metering unit 10 and aninjecting unit 12 for each engine cylinder. The rail unit 11 is anextruded component with internal longitudinaly extending air passage 13,fuel supply passage 14, and fuel return passage 15. These passages areclosed at each end of the rail. At appropriate locations, as seen inFIG. 1, there are provided an air supply conduit connector 9communicating with the air passage 13, a fuel supply conduit connector 6communicating with the fuel supply passage 14, and a fuel return conduitconnector 3 communicating with the fuel return passage 15 via a pressureregulator as hereinafter described.

The fuel metering unit 10 is a commercially available component and willnot be described in detail herein. A suitable commercially availablemetering unit is that marketed by Rochester Products Division of GeneralMotors Corporation under the Trade Mark "Multec". A fuel inlet port 16and a fuel outlet port 17 are provided in the body 18 of the meteringunit 10 to permit the flow of fuel therethrough, and a metering nozzleis provided in the area 19 to deliver fuel to the passage 20, ashereinafter described.

The body 18 of the metering unit 10 is received within a lateral bore 26provided in the external wall 21 of the rail unit 11, with an "O" ringseal 22 between the body 18 and the bore 26, and a further "O" ring seal23 between the body 18 and the bore 27 in the internal wall 25 betweenthe air passages 13 and fuel supply passage 14. The position of thenozzle area 19 of the metering unit 10 with respect to the passage 20 iscontrolled by the clamp plate 28 received in the recess 29 provided inthe body 18. The clamp plate 28 is held against the wall 21 by asuitably located bolt or set screw (not shown). The body 18 of themetering unit passes through the wall between the passages 14 and 15 at34 with a close tolerenced fit so fuel leakage therebetween is veryrestricted.

The injecting unit 12 as seen in FIG. 3 has a housing 30 with acylindrical spigot 31 projecting from the lower end thereof with aninjection port 32 therein communicating with an internal cavity 33. Thepoppet valve head 34, which co-operates with the port 32, is secured tothe tubular valve stem 35. The tubular valve stem 35 is slidablysupported in the cavity 33 by guide ribs 36 spaced equally about theperiphery of the valve stem 35.

The solenoid coil 40 is located in the housing 30 concentric with thetubular valve stem 35 and is retained between the base 37 of the housing30 and the coverplate 38. The solenoid armature 41, affixed to the upperend of the tubular valve stem 35 has limited axial movement as indicatedby the gap 39 and is urged in an upward direction by the spring 42 tonormally maintain the valve head 34 in a closing relation with the port32. The lower end of the valve stem 35 is provided with opposedapertures 43 to provide constant communication between the interior ofthe stem 35 and the cavity 33. Energising of the solenoid coil 40 drawsthe armature 41 downward to close the gap 39, thereby displacing thestem 35 and valve head 34 to open the port 32.

The cover plate 38, being the upper end of the housing 30, is receivedin the bore 45 in the rail unit 11 so that the bore 48 at the upper endof the armature 41 receives the tube 46 mounted in the rail unit 11. Thetube 46 is a sealed press fit in passage 20 formed in the wall 25, ofthe rail unit 11, and directs the fuel from the passage 20 into the openupper end of the valve stem 35.

Attached to the end of the metering unit 10 which is located in the bore27 in the wall 25 of the rail unit 11 is an air flow control ring 75.The annular flange 74 of the air flow control ring 75 fits over themetering unit body 18. In the external face of the flange 74 is anannular groove 77 which communicates with the passage 78, and via theseries of apertures 79 with the interior cavity 80 of the ring 75. Asseen in FIG. 4 of the drawings, the end of the ring 75 has a centralfuel passage 81 defined by the collar 82, which is secured to theperipheral portion of the ring 75 through the three equally spaced arms84. The spaces defined between the periphery of the ring 75, the centralcollar 82 and the three arms 84 define three arcuate openings 85 for theflow of air from the air passage 13.

As seen in FIG. 2, the passage 88 communicates the air passage 13 withthe annular cavity 80 about the collar 82 whereby air from the airpassage 13 may pass through the passage 88 and the arcuate openings 85and hence into the internal cavity 80 within the ring 75. This air canthen pass adjacent the nozzle area 19 into the fuel passage 81 throughthe collar 82. It will thus be seen that when the fuel injection systemis in operation air may pass from the air passage 13 to establish aradially inward flow around the area 19 of the metering unit 10, fromwhich the metered quantity of fuel is delivered, and that air will thenmove axially through the passage 81 into the passage 20 to then passthrough the tube 46 into the hollow interior of the valve stem 35. Thisform of air flow will inhibit the loss of fuel by a back flow throughthe passage 88 into the air passage 13.

The annular groove 77, apertures 79 and passage 78, provide asubstantially unrestricted flow path for air from the air passage 13into the bore 49 in the cover plate 38. From the bore 49 the air mayenter the hollow valve stem 35 and also pass between the externalsurface of the armature 41 and the sleeve 47, through the gap 39 andinto the cavity 33. This communication between the air passage 13 andthe cavity 33 maintains an air flow and a pressure in the cavity 33sufficient to prevent an accumulation of fuel in, or a back flow of fuelfrom, the cavity 33 past the armature 41 that could detract from theaccuracy of the fuel metering to the engine.

The sleeve 47 is outwardly flanged at 58 to seat on the base of the bore49 in the cover plate 38. The lower end of the sleeve 47 is locatedbetween the neck 50 of the housing 30 and the extension 51 of the spigot31. These three components are welded together in the area ofoverlapping relation to form a fuel and air tight junction.

The apparatus as above described is intended to be used on amulti-cylinder engine as shown in FIG. 1 with the single air and fuelrail unit 11 having assembled thereto a metering unit 10 and injectingunit 12 for each cylinder of the engine. As seen in FIG. 5 the spigot 31of the injecting unit 12 is received in an appropriate stepped bore 57in the engine cylinder head 2 so that the fuel delivered through theport 32 will directly enter the cylinder combustion chamber 44. The sealring 6, located in the spigot 31 will seal against an appropriatesurface of the cylinder head. Suitable clamping arrangements, such asthe bolts 8, are provided to secure the rail unit 11 to the cylinderhead 2, so that the rail unit 11 is held in assembly with the injectingunits 12, and the injecting units are in turn held in assembly with thecylinder head. The "O" ring 52 located in the bore 49 forms a sealbetween the rail unit 11 and the flange 58 of the sleeve 47 to preventleakage of fuel or air between the rail unit 11 and the injecting unit12.

As can be seen in FIG. 5, the engine cylinder head has coolant cavitiesand passages 53, 54 and 55, and a spark plug opening 56. The injectionunit 12 received within a stepped bore 57, has part of the housing 30disposed within the coolant cavity 54, so as to provide direct coolingof the injection unit to dissipate the heat generated by the solenoidcoil 40 and to limit the transfer of heat from the combustion chamber tothe injector unit and metering unit.

In FIG. 8 there is provided a modified construction of the air controlring 75 as described with reference to FIG. 2. In the construction shownin FIG. 8 the sleeve 110 and fuel guide tube 114 replace the fuelcontrol ring 74 and collar 82.

It is to be noted that the provision of the sleeve 110 is a modificationto the previously disclosed construction. The sleeve 110 is a close fit,preferably a light interference fit in the bore 111 in the rail unit 11,with the portion 109 of the fuel metering unit 10 a close fit in thesleeve 110. The `O` ring 112 prevents leakage of fuel from the fuelsupply passage 14.

The delivery nozzle of the fuel metering unit 10 is located at 113, inalignment with the fuel guide tube 114 formed integral with the sleeve110, and delivers the metered quantity of fuel into the fuel cavity 120.The fuel injecting unit 12 is in communication with the cavity 120 toreceive the fuel therefrom and is of the same construction as previouslydescribed with reference to FIG. 2.

The cavity 120 is in communication with the air passage 13 via the bore121, annular passage 122 surrounding the fuel guide tube 114, and thearcuate passage 124 therebetween. The bore 121 and the outer wall of theannular passage 122 are formed by respective parallel holes drilledprior to assembly of the fuel metering unit 10 and sleeve 110, and thearcuate passage 124 is formed by machining away portion of the wallbetween these two holes. As a result of these machining operations, thewall portion 125, between the two holes is retained and extends toover-lap part of the fuel guide tube 114, and a part conical surface 126extending over an arc of 180° is formed. It is to be noted that thecavity 120, bore 121, annular passage 122 and arcuate passage 124 areindividual to each metering and injecting units 10 and 12, where thefuel supply and return passage 14 and 15 and air supply passage 13 arecommon to all such units. The inclination of the surface 126 will directfuel rebounding thereoff towards the injecting unit 12 rather thandirectly back towards the annular passage 122.

In use, during a fuel injection phase, an air flow exists from thepassage 13 through the bore 121 arcuate passage 124 and annular passage122 into the cavity 120, and on through the cavity 120 to the fuelinjecting unit 12. This air flow carries the fuel that has beendelivered into the cavity 120, by the fuel metering unit 10, into andthrough the fuel injecting unit 12 to deliver it to the engine.

It is not uncommon to deliver the fuel, or at least part thereof, intothe cavity 120 prior to the commencement of the injection of fuel intothe engine, that is at a time when there is substantially no air flowinto the cavity 120 from the air passage 13. The above describedarrangement of the bore 121 and passages 122 and 124 are such that atortuous path is presented to any fuel that may otherwise have atendency to flow back from the cavity 120 into the air passage 13. Alsofuel droplets rebounding off the surfaces of the cavity 120, afterissuing from the metering unit 10, have a high probability of strikinganother wall of the cavity or of the annular passage 122, and sodissapate their kinetic energy and/or be directed on a path that willavoid escape of the fuel into the air passage 13. The use of an annularpassage, as in annular passage 122, to provide the only point of entryof any fuel from the cavity 120 to a path to the air passage 13, has theadvantage of providing a relatively unrestricted flow area for the airpassing to the cavity but presents a narrow opening to fuel dropletspassing in the reverse direction.

The prevention of the escape of fuel from the cavity 20 in FIG. 2 or 120in FIG. 8 to the air passage 13 has the advantage of improving theaccuracy of metering the fuel to the engine with resultant improvementsin fuel efficiency and emissions control of the engine, and avoidance offuel accumulation in the air passage and the problem of purging thereof.

As the fuel is delivered from the metering unit 10 into the passage 20against the air pressure which exists therein, being substantially thepressure in the air passage 13, it is necessary to regulate the fuelpressure with respect to the air pressure to obtain the requiredaccuracy in the metering of the fuel. As a plurality of metering andinjecting units are incorporated in the single rail unit 11, theprovision of a single regulator, also incorporated into the rail unit11, can provide the required pressure regulation for all metering andinjecting units.

A typical construction of a regulator unit is depicted in FIG. 6 of theaccompanying drawings. The regulator unit 60 comprises a body 61 havinga fuel portion 62 and an air portion 63 secured together by the swagedflange 64. The fuel portion 62 is a close fit in the bore 56 thatextends through the external wall 21 of the rail unit 11 and alsothrough the wall 74 between the fuel supply passage 14 and the fuelreturn passage 15. The fuel return passage 15 communicates with thehollow interior of the fuel portion 62 through apertures 59 in theperipheral wall of the fuel portion 62. An "O" ring seal 65 is providedbetween the fuel portion 62 of the body 61 and the wall of the rail unit11. The fuel portion 62 also extends partly into the wall 25 between thefuel supply passage 14 and the air passage 13 with the air portion 63extends through the remainder of the wall 25 into the air passage 13.

The diaphragm 66 is clamped between opposite shoulders on the fuelportion 62 and air portion 63 so as to form a barrier between the fueland the air, but may flex in the normal manner of a diaphragm. Thepre-load spring 67 acts against the pressure plate 68 secured to thediaphragm 66 and the force applied by the spring can be controlled bythe adjusting plug 69, which has an aperture therethrough to communicatethe air passage 13 with the interior of the air portion 63.

The pressure plate 68 carries a valve disc 70, which co-operates withthe port sleeve 71, which defines the port 72. The body 61 is providedwith a suitable threaded aperture 73 to which a fuel return connector 3may be fitted to return released fuel to a fuel reservoir. As seen inmore detail in FIG. 7, the valve disc 70 may be of a form having anintegral spherical head 90 received in a conical cavity 91 in thepressure plate 68. The head 90 is held in assembly by the retainer plate92, that is secured about the periphery by the swaged rim 93 of thepressure plate 68. The retainer plate 92 has a slot extending to theperiphery thereof from the central opening 94 to permit entry of theneck portion 95 into the central opening 94. The spring 96 urges thespherical head 90 toward the retainer plate 92 to maintain the centrallocation of the valve disc 70. This construction improves the accuracyof the sealing of the valve disc 70 with port sleeve 71.

It is to be understood that the construction of the regulator abovedescribed may be varied by having the port sleeve 71 attached to thediaphragm 66 and the valve disc stationary.

In use, if the fuel pressure remains below the pressure represented bythe combined affect of the air pressure on the diaphragm 66 and the loadapplied by the spring 67, the valve plate 70 will remain in the positionas shown closing the port 72. However, if the fuel pressure rises to alevel sufficient to overcome the combined load of the air pressure andspring 67 on the diaphragm 66, then the diaphragm will deflect to theright as shown in the drawing, thereby displacing the valve disc 70 toopen the port 72. The fuel released through the port 72 is returned tothe fuel reservoir.

The above described construction results in the regulator device beingsubstantially contained within the confines of the rail unit 11 and thusdoes not in real terms contribute to an increase in the overalldimensions of the engine and fuel injection system. Also in thisconstruction the volume of fuel within the rail unit damps the pressurefluctuations arising from the operation of the regulator.

It is to be understood that the fuel injection system as above describedmay be used in respect of any form of internal combustion engine,including engines operating on either the four stroke or two strokecycle. Such engines incorporating the fuel injection system abovedescribed are particularly suitable for use in all forms of vehicleengines, including engines for aircraft, land vehicles and marineapplications, the latter including outboard marine engine.

The claims defining the invention are as follows:
 1. A fuel injectionsystem for a multi-cylinder internal combustion engine comprising arigid elongated unitary member having formed therein a gas supply duct,a fuel supply duct and a fuel return duct, each said duct extending inthe direction of elongation of the unitary member and each adapted forconnection to a gas supply, a fuel supply and a fuel returnrespectively, at least one fuel metering and injecting apparatus foreach cylinder of the engine each integrated with the unitary member andeach comprising a fuel metering means and a fuel injecting means, thefuel metering means being adapted to deliver metered quantities of fuelto the fuel injecting means, each fuel metering means being incommunication with the fuel supply and fuel return ducts so that in usefuel can be circulated through each fuel metering means, and each fuelinjecting means being in communication with the gas duct andcommunicable with a respective cylinder of the engine, each said fuelinjecting means being adapted to effect delivery of the metered quantityof fuel entrained in gas supplied from the gas duct for delivery to thecylinder.
 2. A fuel injection system as claimed in claim 1 wherein arespective fuel cavity is provided in the unitary member to interactwith each fuel metering and injection apparatus, the fuel cavity beinglocated to receive the metered quantity of fuel delivered from the fuelmetering means and is in communication with the fuel injecting means,said cavity is also in communication with the gas duct, whereby when thefuel injecting means is in communication with the engine, gas from thegas duct flows through the cavity and fuel injecting means to transportthe metered quantity of fuel to the engine cylinder.
 3. A fuel injectionsystem as claimed in claim 2 wherein a conduit extends from the fuelmetering means to the fuel cavity, the conduit being located so themetered quantity of fuel passes from the fuel metering means through theconduit into the fuel cavity.
 4. A fuel injection system as claimed inclaim 3, wherein the conduit adjacent the location of the entry of thefuel thereinto communicates with the gas duct so that gas passes throughthe conduit to enter the fuel cavity.
 5. A fuel injection system asclaimed in claim 4 wherein the conduit extends through an opening in thewall of the fuel cavity, said conduit defining with said opening anannular passage about the conduit, said annular passage providingcommunication between the gas duct and the fuel cavity, whereby gasflows through the annular passage into the fuel cavity.
 6. A fuelinjection system as claimed in claim 4 wherein the fuel cavity isconfigured to present an inclined face opposite the location of theentry of the fuel into the fuel cavity, said face being inclined to thetrajectory of the incoming fuel so the fuel rebounding from saidinclined face is directed toward the fuel injecting means.
 7. A fuelinjection system as claimed in claim 4 wherein a gas cavity is providedabout the conduit, said gas cavity being in communication with the gasduct, and apertures are provided about the periphery of the conduitadjacent the fuel metering means communicating the gas cavity with theinterior of the conduit.
 8. A fuel injection system as claimed in anyone of claims 2-7 wherein the fuel injecting means comprises a bodyhaving an axial bore with a valve controlled delivery port at one end,and communicating at the other end with the fuel cavity in the unitarymember, and including electromagnetic means mounted in the body co-axialwith the axial bore and operable to selectively open and close saiddelivery port.
 9. A fuel injection system as claimed in claim 8 whereinthe valve controlled delivery port includes a valve element adapted tosealably engage the delivery port, a hollow valve stem secured at oneend to the valve element, said valve stem extending co-axially alongsaid bore, and means arranged to direct fuel from the fuel cavity intothe other end of the hollow valve stem.
 10. A fuel injection system asclaimed in claim 9 wherein the electromagnetic means comprises astationary solenoid coil located concentrically about the hollow valvestem, and an armature secured to the hollow valve stem adjacent saidother end thereof.
 11. A fuel injection system as claimed in claim 9wherein the hollow valve stem has an aperture in the wall thereofadjacent the valve element to permit fuel to pass from within the hollowvalve stem into the axial bore for delivery through the delivery port.12. A fuel injection system as claimed in claim 9, wherein means areprovided to communicate the bore in the body of the fuel injecting meanswith the gas duct independently of the communication through the hollowvalve stem, whereby during delivery of fuel through the delivery port,further gas flows through said communication means and said bore to thedelivery port.
 13. A fuel injection system as claimed in any one ofclaims 1, 2, 3, 4, 5, 6 or 7 wherein the injecting means includesselectively openable valve means to establish direct communicationbetween a respective cylinder of the engine and the gas duct.
 14. A fuelinjection system as claimed in claim 13 wherein the fuel injecting meanscomprises a body having an axial bore with a valve controlled deliveryport at one end, and communicating at the other end with the fuel cavityin the unitary member, and including electromagnetic means mounted inthe body co-axial with the axial bore and operable to selectively openand close said delivery port.
 15. A fuel injection system as claimed inclaim 13 wherein the fuel supply duct and fuel return duct are in a sideby side relation with a first internal wall therebetween, each fuelmetering means having a body with spaced fuel inlet and fuel outletports therein, each fuel metering means being mounted in the unitarymember with the body thereof passing through an external wall of theunitary member and said first internal wall with the fuel inlet portcommunicating with the fuel supply duct and the fuel outlet portcommunicating with the fuel return duct.
 16. A fuel injection system asclaimed in claim 15 wherein each fuel injecting means is mounted to theunitary member to project from a further external wall thereof in adirection inclined to the direction of projection into the unitary bodyof the associated fuel metering means.
 17. A fuel injection system asclaimed in claim 16 wherein the fuel injection means projects in adirection at right angles to the direction that the fuel metering meansprojects into the unitary member.
 18. A fuel injection system as claimedin claim 15, wherein the external wall and the first internal wall aregenerally parallel and the body of the fuel metering means extendsthrough said external and first internal walls substantially at a rightangle thereto.
 19. A fuel injection system as claimed in claim 15wherein a second internal wall in the unitary member separates the fuelsupply duct from the gas duct, the fuel cavity being at least partlyformed in said second internal wall, and the body of the fuel meteringmeans extends into said second internal wall to communicate with thefuel cavity to deliver fuel thereto.
 20. A fuel injection system asclaimed in claim 19 wherein the fuel injection means projects in adirection at right angles to the direction that the fuel metering meansprojects into the unitary member.
 21. A fuel injection system as claimedin claim 13 including pressure regulator means mounted to extend intothe unitary member to communicate with the gas duct and one of the fuelsupply and return ducts, said pressure regulator means being adapted toin use maintain a predetermined pressure differential between the gas inthe gas duct and the fuel in the fuel supply duct.
 22. A fuel injectionsystem as claimed in claim 21 wherein the regulator means is adapted tocontrol the rate of flow of fuel from the fuel return duct to a fuelreservoir in relation to the pressure in the gas duct to maintain saidpredetermined pressure differential.
 23. A fuel injection system for aninternal combustion engine comprising a body having an internal portcavity, a port in the body providing communication with the port cavityfrom the exterior of the body, valve means including a valve elementadapted to co-operate with the port to close same and a valve stemattached to the valve element and extending through the port cavity,electromagnetic means within the body disposed about and operablyconnected to the valve stem whereby the valve element is moved to openand close the port when the electromagnetic means is selectivelyenergised and de-energised, a passage through the valve stemcommunicating the port cavity with a fuel cavity located at that side ofthe electromagnetic means opposite to the port, metering means toselectively deliver fuel to the fuel cavity, and means to supply gas tothe fuel cavity at least when the port is open to convey fuel from thefuel cavity through the valve stem passage and the port cavity to andthrough the open port.
 24. A fuel injection system as claimed in claim23 wherein the injecting means includes selectively openable valve meansto establish direct communication between a respective cylinder of theengine and the gas duct.
 25. A fuel injection system as claimed in claim23 or claim 24 wherein the electromagnetic means comprises a stationarysolenoid coil located concentrically about the valve stem; and anarmature secured to the valve stem adjacent said other end thereof. 26.A fuel injection system as claimed in claim 25 wherein the armature islocated substantially within an annular space formed between the valvestem and the solenoid coil.
 27. A fuel injection system as claimed inclaim 26 wherein the valve stem extends through the solenoid armature tocommunicate with the fuel cavity, said valve stem having apertures inthe wall thereof adjacent the valve element to permit fuel to thepassage within the valve stem into the port cavity.